Full name: Hebeloma pallidomarginatum (Peck) Sacc. (1887)
Published: Syll. Fung. 5: 804 (1887)
Taxonomic status: This is a Naucoria.
Notes: Current name: Naucoria pallidomarginata (Peck) Murrill, North American Flora 10 (3): 178 (1917).

Basionym: Agaricus pallidomarginatus Peck [as "Agaricus (Hebeloma) pallidomarginatus"] (1873)

Types: UNITED STATES: New York: Rensselaer, Sandlake (approx. 42.6373°N, 73.5407°W, alt. approx. 240 m a.s.l.) on boggy soil in bog, Sep. 1871, C.H. Peck (Lectotype. herbarium acc. no. NYS-F-002220, HJB1000262; Isotype. herbarium acc. no. K(M)153651, HJB1000227). Lectotype designated by Eberhardt et al., Mycologia 114 (2): (2022) page 381 (MBT10000869).

Homotypic synonyms: Derminus pallidomarginatus (Peck) Henn. [as "pallido-marginatus"] (1898)

Diagnosis: Pileus brittle, broadly convex, sometimes irregular, smooth, hygrophanous, brown with a pale margin when moist, ochraceous und subatomaceous when dry; lamellae close, thin, rounded and slightly emarginate at tho stem, tapering outwardly, ochraceous-brown; stem usually long and flexuous, equal or tapering upward, hollow, a little paler than the pileus, white-floccose at the base; spores subelliptical, .0004' long, .0002' broad. Plant gregarious, 1'-3' high, pileus 6"-12" broad, stem 1“ thick. Ground in swamps and wet places. Sandlake. September.

Commentary: This taxon was originally described by Peck (1873b) as Agaricus (Hebeloma) pallidomarginatus and recombined as Hebeloma pallido-marginatum by Saccardo (1887). The type material at the New York State Museum is in three parts. Two parts have accession number NYS-F-002220, one part is labelled as Aug (NYS-F-002220.2). while the second part is labelled as Sept. (NYS-F-002220.1); there is also a note “Hebeloma, mixed with a pink spored species, CHK”. The third part has accession number NYS-F-002221 and was not examined during this study but has a note attached: “Agaricus (Hebeloma) pallidomarginatus Pk. Spores 8-12 × 5-7 μ[m] minutely echinulate, a few up to 15 × 8μ[m]. Perhaps the larger ones have fallen from plants that were mixed with these. Cystidia long, acuminate, slender, broadly ventricose. G.F.A. Apr. 18 1918.”. Following examination, the two parts of NYS-F-002220 appear to represent the same species, but only the lectotype is collected in the month (September) specified in the original description. The spores are yellowish brown, distinctly ornamented and nondextrinoid with a distinctly loosening perispore in a few spores, on average 9 × 5.5 μm. The cheilocystidia are ventricose, lanceolate and acuminate, typical of Naucoria species. Unfortunately, no DNA sequence information could be obtained. From the note attached by G.F. Atkinson to NYS-F-002221, it would appear likely that this also represents the same species. A collection annotated as isotype of Agaricus pallido-marginatus Peck, Herb. C.B. Plowright exists in herbarium K. This collection has been examined and appears to belong to Entoloma s.l., so may represent the pink-spored species mentioned in the herbarium note. Hence, the part of collection of NYS-F-002220.1 labelled as Sept. was selected as lectotype. Murrill (1917) considered N. paludosa (Peck 1888) and “N. uliginosa Peck 1900” (Peck 1902) as synonyms of N. pallidomarginata. Naucoria paludosa appears to be the oldest name. Naucoria uligionsa shares its type locality and collecting month with N. pallidomarginata. Naucoria paludosa is the only one of these taxa that has been transferred to Alnicola (Singer 1977). The original descriptions of A. pallidomarginatus, N. paludosa and N. uliginosa could refer to the same taxon, but as we have not examined type material of N. paludosa or N. uliginosa, hence, we cannot verify Murrill’s (1917) synonymization.